Base drag reduction for road vehicles and &#39;airdrop&#39; cargo aircraft

ABSTRACT

Methods providing naturally driven routing of air bleed derived from the external air pressure field typically developed about a moving vehicle were conceived. By design, internal ductways are to be used for providing an open flow path from relatively higher air pressure sources (such as that in the undercarriage region of a driven car) into lower base pressure regions (typically developed aft of blunt trailing body regions) as are generally found on road and ‘airdrop’ cargo delivery air vehicles having open rear doors. Low energy air bleed flow injected into the vehicle&#39;s separated afterbody region acts to replenish entrained base flow and its base drag reduction is thereby achieved.

BUSINESS PROBLEM THAT LED TO THIS INVENTION

Due to the lack of adequate supplies of refined hydrocarbon fuels relative to increased global demand and high usage, the cost of gasoline for the powering of typical road cars and trucks has escalated. Higher fuel costs in the USA are driven by foreign nations that control the global rates of oil production. In addition, domestic oil refineries have been limited in their production usage by recent hurricane damage inflicted upon these facilities. Also, politically driven global markets are often constrained by controlled foreign oil supplies so that higher costs of hydrocarbon fuels can be derived. Consequently, road and air travel in the USA is largely being self-curtailed to special needs and shortened trips so that the costs of travel can be alleviated. By limiting normal mileage usage, drivers and fliers are striving to realize savings in their fuel costs. Accordingly, significant reductions in merchant sales and lesser profits are being imposed upon our roadside businesses. Further, added transportation expenses due to higher fuel costs necessary for rapid interstate trucking transportation as well as shorter road deliveries of their goods are causing many small businesses to hesitate in their plans to avail new job opportunities to our national work force. This disruption in car and aircraft usage is being felt across our nation and these factors act to weaken the growth of our national economy.

TECHNICAL PROBLEMS SOLVED BY THE INVENTION

The rate of fuel consumption used by a standard car or truck can be alleviated by introducing unique air injection approaches to road vehicle afterbody designs. In particular, a typical notch-backed car suffers high base drag contributions in two local regions; namely, its separated afterbody base flow regions (see FIG. 1).

BRIEF DESCRIPTION OF INVENTION Basic Drag Reduction Technique for Traveling Vehicles

A unique technique for achieving base drag reduction of a traveling road vehicle has been conceived. Via internal routing by ducts to an aft located plenum chamber within a traveling road vehicle, sources of low energy airflow (having encountered drag losses due to blunt shaped undercarriage components) can be self-driven (unpowered) from selected higher pressure air regions into lower base pressure regions of blunt afterbody shaped vehicles. In the influence of air particle entrainment away from the vehicle's base region (induced by local separation of the vehicle's external afterbody flow), low base pressure develops and this imposes high base drag upon the vehicle. By distributing an injection of low energy airflow (derived from the vehicle's undercarriage into the vehicle's base region), air bleed at low injection speeds into the vehicle's base flow region can be achieved. In this manner, the entrained air particles of the base flow can be replenished, thereby significantly reducing the vehicle's base and total drag. Note that only low energy air bleed sources can be effectively used for the distribution of base injection into a vehicle's base region so as to successfully effect base drag reduction. Such sources can be taken and routed from the undercarriage regions of a road vehicle; wherein separated flow regions can readily be tapped from downstream of blunt and irregular shaped components (such as bent pipes, rods, compressors, fuel pumps, etc.); wherein such momentum losses have already been suffered.

Note that high energy sources of attached airflow developed around a road vehicle (largely devoid of viscous and flow separation losses) should be avoided because local airflow injections into the vehicle's base region of this kind can act to enhance the undesired entrainment process. The use of self-injection techniques that deliver low energy air bleed into the separated base flow of a traveling car's blunt afterbody (FIG. 2) can be used to raise its base pressure and realize significant base drag reduction; thereby total drag reduction to the vehicle can be achieved.

DESCRIPTION OF FIGURES

FIG. 1—High base drag on a typical road vehicle due to afterbody flow separation I. Unsteady vortex shedding formations 2 are shown.

FIG. 2—Base drag reduction for road vehicles can be achieved due to injection of air bleed 3 that is distributed into separated afterbody flow regions. 

1. To provide base drag reduction and thereby fuel savings to a traveling road vehicle configured with blunt based afterbody regions by injecting a distribution of low energy air bleeds (taken from the underbelly flow regions of the vehicle and ducted into the separated base flow regions of the vehicle). 